The term "aluminum" as used herein and in the claims includes pure aluminum and aluminum alloys.
JP-B-45300/1991 discloses a condenser for use in air-cooling systems for motor vehicles which comprises a pair of headers arranged at right and left in parallel and spaced apart from each other, parallel flat refrigerant tubes each joined at its opposite ends to the two headers, corrugated fins arranged in air flow clearances between the adjacent refrigerant tubes and brazed to the adjacent refrigerant tubes, an inlet pipe connected to the upper end of the left header, an outlet pipe connected to the lower end of the right header, a left partition provided inside the left header and positioned above the midportion thereof, and a right partition provided inside the right header and positioned below the midportion thereof, the number of refrigerant tubes between the inlet pipe and the left partition, the number of refrigerant tubes between the left partition and the right partition and the number of refrigerant tubes between the right partition and the outlet pipe decreasing from above downward. A refrigerant flowing into the inlet pipe in a vapor phase flows zigzag through the condenser before flowing out from the outlet pipe in a liquid phase. Condensers of the construction described are called parallel flow or multiflow condenser, realize higher efficiencies, lower pressure losses and supercompactness and are in wide use recently in place of conventional serpentine condensers.
It is required that the flat refrigerant tube for use in the condenser have pressure resistance since the refrigerant is introduced thereinto in the form of a gas of high pressure. To meet this requirement and to achieve a high heat exchange efficiency, the refrigerant tube used is in the form of a flat aluminum tube which comprises upper and lower walls, and a reinforcing wall connected between the upper and lower walls and extending longitudinally.
However, the reinforcing wall provided in the refrigerant tube forms independent parallel refrigerant passages in the interior of the tube. Air flows orthogonal to the parallel refrigerant passages, so that the heat exchange efficiency is consequently higher in the refrigerant passage at the air inlet side than in the passage at the air outlet side. Accordingly, gaseous refrigerant is rapidly condensed to a liquid in the refrigerant passage at the upstream side, whereas the refrigerant still remains in the passage at the downstream side. When the entire structure of the tube is considered, the refrigerant therefore flows unevenly, failing to achieve a high heat exchange efficiency.
The object of the present invention is to provide a refrigerant tube for use in heat exchangers which achieves a high heat exchange efficiency.